TNO Develops Novel CO₂ Purification Method for Industrial Use | Alcircle

The quest for efficient carbon capture and storage (CCS) technologies has led researchers in the Netherlands to develop a novel method for purifying carbon dioxide (CO₂) streams, a critical step in making the process viable for large-scale deployment. The technology, spearheaded by the Netherlands Organisation for Applied Scientific Research (TNO), focuses on removing carbon monoxide (CO) – a common impurity – from CO₂ intended for either long-term geological storage or reuse in industrial applications. This purification is essential because even small amounts of CO can compromise the integrity of pipelines, storage sites, and catalysts used in subsequent CO₂ utilization processes.

Currently, existing CO₂ purification methods often come with significant drawbacks, including high energy consumption, complex operational requirements, or the introduction of additional contaminants. The TNO approach aims to address these limitations through a process called chemical cycling, utilizing metal oxide particles as oxygen carriers. This method offers a potentially more energy-efficient and cleaner alternative to existing technologies.

How the Metal Oxide Cycling Process Works

The core of the TNO technology lies in a two-stage process. In the first stage, a gas mixture containing both CO₂ and CO is passed over a bed of metal oxide particles. These oxides are designed to release oxygen, which then reacts with the CO, converting it into CO₂. This reaction simultaneously reduces the metal oxide, partially depleting it of oxygen.

The second stage involves re-oxidizing the reduced metal oxide by exposing it to air. This restores the oxide to its original state, ready for another cycle of CO removal. Crucially, this process doesn’t introduce any new substances into the gas stream, ensuring a high-purity CO₂ output. The researchers emphasize that the process is designed to remove CO without adding other substances to the gas stream, a key advantage over some existing purification methods.

The selection of appropriate metal oxides was guided by thermodynamic analysis. The team evaluated oxides of nickel, copper, manganese, and iron, focusing on performance at temperatures below 700°C and low CO concentrations – conditions typical of industrial CO₂ capture scenarios. Copper and iron oxides demonstrated the most promising results, exhibiting greater stability compared to nickel and manganese oxides. Notably, both stages of the process generate heat, suggesting the potential for energy recovery and integration with other industrial processes, such as steam or electricity generation.

Iron Oxide: A Promising Material for CO Purification

Given its abundance, low toxicity, and cost-effectiveness, iron-based materials received particular attention during the research. Several iron oxide formulations supported by aluminium oxide were tested, with one sample – produced using an infusion method – proving particularly effective. This sample maintained stable performance for approximately 200 cycles at temperatures ranging from 400 to 550°C, efficiently converting CO to CO₂. The system also demonstrated effectiveness at CO concentrations of 2,000 to 4,000 ppm, levels commonly found in industrial gas streams. Rio Tinto’s advancements in metal extraction highlight the broader industry focus on efficient resource utilization and purification processes.

Experiments revealed a nuanced relationship between temperature and conversion time. Increasing the temperature to around 450°C increased the time required for complete CO conversion, with further temperature increases yielding only marginal improvements. This suggests an optimal operating temperature exists, dependent on the specific process design and how the generated heat is utilized.

Implications for Carbon Capture and Storage

The development of this technology has significant implications for the broader field of carbon capture and storage, particularly within the context of industrial decarbonization. Effective CO₂ purification is paramount for ensuring the safe and efficient long-term storage of captured carbon, as well as for enabling the use of CO₂ as a feedstock in various industrial processes. The aluminium industry, for example, is actively exploring CO₂ utilization pathways, and high-purity CO₂ streams are essential for these applications. The global aluminium industry outlook for 2026 anticipates increased demand for sustainable practices, including CCS technologies.

While iron-based materials showed strong performance, the researchers acknowledge that other materials may offer even faster reaction rates or greater durability. Future research will focus on exploring a wider range of materials and conducting comprehensive technical and economic feasibility studies, comparing the TNO method to established techniques like cryogenic separation (which is energy-intensive) and catalytic oxidation (a chemical process relying on catalysts).

Challenges and Future Directions

The TNO research represents a promising step forward in CO₂ purification technology, but several challenges remain. Long-term stability and durability of the metal oxide materials demand further investigation. Scaling up the process from laboratory experiments to industrial-scale operation will require careful engineering and optimization. A thorough life cycle assessment is needed to fully evaluate the environmental impact of the technology, considering factors such as material sourcing and energy consumption.

The team’s next steps involve testing additional materials and conducting detailed economic analyses to determine the competitiveness of the process compared to existing purification methods. They also plan to explore potential synergies with other industrial processes, leveraging the heat generated during the chemical cycling process to improve overall energy efficiency. TNO’s Sorption Enhanced Water Gas Shift (SEWGS) technology, which focuses on CO₂ reduction, demonstrates the organization’s broader commitment to developing innovative solutions for a more sustainable future.

Recent discoveries regarding the presence of CO and CO₂ ices in the outer solar system, as revealed by the James Webb Space Telescope, as reported by the University of Central Florida, underscore the importance of understanding the behavior and properties of these gases in various environments, further motivating research into efficient capture and purification technologies.