3D-Printed Adsorbents and Catalysts for Carbon Dioxide Capture and Conversion

Abstract

Conventional adsorbents and catalysts in powder form often face limitations such as poor gas diffusion, high pressure drop, and challenges in scalability. To overcome these issues, structured forms like pellets or monoliths are used, but traditional shaping methods fail to provide adequate control over geometry and porosity, limiting their performance in adsorption and catalysis applications. This dissertation explores the use of advanced 3D-printing techniques to fabricate structured adsorbents and catalysts with gyroid (triply periodic minimal lattice) geometry, enabling enhanced CO2 capture and conversion efficiency.

In the first part of this work, stereolithography (SLA)-based 3D-printed polymer gyroid scaffolds were coated with zeolite 13X, a material known for its excellent CO2 adsorption capacity. The primary and secondary coated samples showed significant improvements in CO2/N2 selectivity (569 and 536 at 50 mbar for 2-S3DPP and 1-S3DPP, respectively) compared to zeolite 13X powder (294 at 50 mbar). Equilibrium adsorption kinetics were also enhanced, with coated samples reaching 4 mmol g⁻¹ in under 62 minutes, compared to 110 minutes for the powder. Building upon these results, all-zeolite monoliths were fabricated using digital light processing (DLP) and sintered to improve mechanical strength and adsorption performance. The monoliths achieved faster equilibrium adsorption times (77 minutes) and exhibited lower pressure drops compared to traditional powder or beads, demonstrating the advantages of 3Dprinting in creating high-performance adsorbents.

The next part focused on integrating metal 3D-printing with metal-organic framework (MOF) synthesis. Selective laser melting (SLM) was used to fabricate aluminum alloy (AlSi10Mg) gyroid structures, which were subsequently utilized as templates for the in-situ growth of MIL-96, an aluminum-based MOF. This salt-free synthesis method leveraged the aluminum content of the alloy, yielding monoliths (3DM96) with a CO2 adsorption capacity of 4.23 mmol g⁻¹, surpassing the performance of powder samples (3.63 mmol g⁻¹). While the monoliths demonstrated enhanced adsorption capacity, breakthrough tests indicated mass transfer limitations, which were attributed to differences in crystal morphology. Next, for CO2/CH4 separation, 3D-printed zeolite RHO monoliths were fabricated using DLP. These gyroid structures were either sintered or pyrolyzed, resulting in materials with distinct adsorption behaviors. While the sintered monoliths demonstrated improved CO2/CH4 selectivity due to reduced CH4 adsorption, the pyrolyzed samples exhibited lower selectivity, highlighting the tunability of 3D-printed adsorbents for specific applications.

To address the economic challenges associated of CO2 storage, the work also explored CO2 conversion into methane through catalytic methanation. SLM-fabricated aluminum alloy gyroid structures were wash-coated with Ni/Al2O3 catalysts. These 3D-printed structures offered enhanced heat dissipation and stability, achieving higher CO2 conversion (77.7%) and CH4 selectivity (97.7%) compared to powder-based catalysts under identical conditions.

In summary, this dissertation demonstrated the potential of 3D-printing to fabricate structured adsorbents and catalysts with improved performance metrics for CO2 capture and conversion. By enabling precise control over material geometry and properties, 3D-printing provides a sustainable, cost-effective approach to advancing carbon management technologies, addressing global climate challenges.

Date of Award	8 Dec 2024
Original language	American English
Supervisor	Nahla Alamoodi (Supervisor)