(514b) Highly Efficient System for Direct Air Capture and Conversion of CO2 to Value-Added Chemicals

Carbon dioxide capture and utilization is becoming the key concern for investment in the energy and industrial sector due to ever increasing carbon emissions and growing concerns about climate change among public and government agencies around the world. Direct Air Capture and Conversion has emerged as a leading technology for mitigating elevated CO₂ atmospheric concentrations.

The primary barrier to minimizing the cost of direct air capture of CO₂ is the cost of energy. We are developing a high-performance solid sorbent collector technology and materials that operate at low-temperature and low energy utilization for Direct Air Capture (DAC) of CO₂. The recovered CO₂ is then utilized to produce methane via the Sabatier reaction. This process produces methane and water by reacting CO₂ with hydrogen. The methane generated can be used directly as a fuel or it can be converted into higher molecular weight hydrocarbons which can be transported or stored in liquid form.

Precision Combustion, Inc. (PCI), with support from DOE and NASA Small Business Innovation Research (SBIR) awards, has developed a novel efficient and compact Direct Air Capture System that operates with low energy input, coupled with Sabatier (i.e., CO₂ methanation) reactor based on its Microlith® catalytic technology to convert the captured CO₂ to produce methane.

Our approach demonstrated the capability to achieve efficient CO2 capture from atmospheric air, and high CO₂ conversion and CH₄ selectivity (i.e., ≥90% of the thermodynamic equilibrium values) at high space velocities, low operating temperatures, and low H₂ requirements. The ability to both capture CO₂ and achieve high CH₄ yield was made possible using high-heat-transfer and high-surface-area Microlith catalytic substrates and novel nanosorbent and catalyst development.

For the high space velocity DAC sorbent structure, PCI has developed and patented a short contact time mesh-based substrate, coated with a densified nanostructured sorbent. The combination enables higher surface area per unit volume and decreased bed volume with equivalent effectiveness to other types of monolithic or loose packing, without significant pressure drop penalty leading to substantial energy savings in DAC operation. Additionally, up to twenty times higher mass and heat transfer coefficients are obtainable as compared to other sorbent systems, such as monoliths and pellets, due primarily to boundary layer minimization and break-up, boosting CO₂ removal rates with greater sorbent bed utilization and less bypass inherent to packed beds or monoliths. Our sorbent manufacturing technology allows for adherent and durable sorbent coatings on the Microlith substrate. PCI developed and demonstrated in operation carbon capture systems capable of supplying CO2 to the Sabatier reactor with low energy cost.

PCI’s approach to Sabatier permits reactor operation under exothermic conditions with efficient heat recuperation for high catalyst performance at high space velocities and extended catalyst lifetime. A key advantage is the ability of the reactor to efficiently sustain its temperature during the CO₂ methanation reaction via an efficient heat recuperator and heat exchanger, thus eliminating the need for an external heat source, resulting in minimal power usage during steady state operation.

Using this Sabatier reactor, PCI designed, developed, and demonstrated a stand-alone CO₂ methanation test system for demonstration and performance validation. The versatility of the test system prototype was demonstrated by operating it under H₂-rich (H₂/CO₂ of >4), stoichiometric (ratio of 4), and CO₂-rich conditions (ratio of <4) without affecting its performance and meeting the equilibrium-predicted CH₄ yield and throughput.

In this presentation, the development of the Microlith-based Direct Air Capture Unit and the and CO₂ methanation reactor and the test system assembly for demonstration and performance validation will be discussed.