A CO 2 Direct Air Capture and Conversion (DACC) system has been designed and implemented at laboratory bench scale using up to 100 g of adsorbent material at atmospheric pressure trying to approach industrially relevant levels. The general objective is to process indoor air from buildings and other spaces having CO 2 -rich atmospheres compared to ambient air and subsequently couple the regeneration of the adsorbent with the conversion of the captured CO 2 into methane via the Sabatier reaction. Several microporous adsorbent materials, including zeolites, activated carbon and metal-organic-frameworks (MOFs) were evaluated both at small scale in powder form and in a prototype system, focusing on their CO 2 adsorption and desorption (regeneration) performance. Pelletized zeolite 5A proved to be the most effective sorbent investigated, achieving a breakthrough volume of 792 mL, a dynamic sorption capacity of 6.30 mg CO₂ ·g Zeolite −1 and a saturation sorption capacity of 7.79 mg CO₂ ·g Zeolite −1 for indoor air containing ca . 460 ppm V CO 2 . To valorize the captured CO 2 , desorption was performed using 10 mL·min −1 H 2 stream at 200 ºC. The resulting CO 2 /H 2 mixture was subsequently fed to a downstream fixed-bed catalytic reactor containing a Ru-based catalyst, where complete CO 2 conversion to methane was achieved at 350 ºC. This prototype demonstrates a combined adsorption-catalytic conversion strategy for Power-to-Gas (PtG) applications employing microporous adsorbents and ambient CO 2 as carbon source. • MOFs present good bed efficiency (64% for UTSA-16) but lower saturation capacity than zeolites in powder form. • Pelletized Zeolite 5A exhibits the best bed efficiency (74%) and saturation capacity (7.8 mg·g −1 ) for CO 2 capture. • Regeneration conditions using H 2 as sweeping gas led to H 2 /CO 2 ratios suitable for methanation. • Two-reactor in series configuration proved to be very efficient for CO 2 valorization through methanation.
Sanz et al. (2026) studied this question.