Dual function materials (Ru+Na2O/Al2O3) for direct air capture of CO2 and in situ catalytic methanation: The impact of realistic ambient conditions

A dual function material (DFM) comprised of 1% Ru, 10% Na2O/γ − Al2O3 was studied for combined direct air capture (DAC) of CO2 and catalytic methanation in a temperature swing operation. In the newly proposed operation, the DFM captures CO2 (400 ppm) from air at ambient conditions. The material is then heated in H2 to a temperature sufficient for catalytic conversion of the captured CO2 to renewable natural gas. In this study, we demonstrate high CO2 adsorption capacity and rates at ambient conditions (25 °C); the adsorbed CO2 is then successfully catalytically methanated upon heating in H2. Adsorption was also carried out in humid conditions, more closely simulating ambient air. Adsorption and methane production were greatly improved with stable initial performance. The rate of adsorption is shown to be flowrate-dependent, which is critical for future reactor design. [Display omitted] •DFM (Ru+Na2O/Al2O3) is able to combine DAC and catalytic methanation.•DFM captures CO2 at ambient temperature and catalytically methanates it at T > 175 °C.•10 cycles of dry adsorption and methanation shows stability.•Humid adsorption conditions enhances adsorption and methane production.•Rate of adsorption on DFM is flowrate dependent; critical for reactor design.