Systems Design and Economic Analysis of Direct Air Capture of CO2 through Temperature Vacuum Swing Adsorption Using MIL-101(Cr)-PEI-800 and mmen-Mg2(dobpdc) MOF Adsorbents

Direct air capture (DAC) removes CO2 from the atmosphere and can therefore address sizable nonpoint sources emissions of CO2 such as those from transportation. We propose a five-step temperature vacuum swing adsorption process for direct air capture using solid adsorbents coated as films on monolithic contactors using steam as the stripping agent during desorption. We perform a modeling study and economic assessment for DAC using two metal organic frameworks, MIL-101 (Cr) -PEI-800 and mmen-Mg2 (dobpdc), for which we have experimentally demonstrated film growth on monolith structures. The results indicate minimum energy requirements, and cost estimates are 0. 145 MJ/mol-CO2 and 75–140/t-CO2 for MIL-101 (Cr) -PEI-800, and 0. 113 MJ/mol-CO2 and 60–190/t-CO2 for mmen-Mg2 (dobpdc), respectively. The overall DAC cost is sensitive to adsorbent purchase cost and lifetime as well as cycle parameters such as adsorption and desorption times. We conclude that mmen-Mg2 (dobpdc) has better performance compared to MIL-101 (Cr) -PEI-800 in terms of energy requirements because of its higher capacity and nonlinear isotherm.