(613a) Sorption Enhanced Dimethyl Ether Synthesis: A Novel Approach for Carbon Dioxide Utilization.

With global CO₂ emissions exceeding 37.4 billion tonnes annually, effective utilization strategies are critical to achieving net-zero targets. Achieving net-zero targets requires the removal of 4.1 GtCO₂ annually by 2030, increasing to 6.4 Gt by 2050 [1]. Dimethyl ether (DME) has emerged as a promising hydrogen carrier and renewable energy storage medium, with increasing demand as a cleaner alternative to diesel and liquefied petroleum gas (LPG). The global DME production capacity was 10 million tonnes in 2012, and demand has risen significantly since then [2]. Conventional DME synthesis from syngas typically results in minimal water formation due to the presence of carbon monoxide, which acts as an oxygen scavenger. However, pure CO₂ hydrogenation leads to excessive water formation, thereby limiting CO₂ conversion, DME yield, and catalyst performance. Sorption-enhanced dimethyl ether synthesis (SEDMES) presents a novel approach that selectively removes water in situ to improve reaction performance.

This study investigates the SEDMES process through pure CO₂ hydrogenation using commercial Cu/ZnO/Al₂O₃ and γ-Al₂O₃ catalysts, combined with zeolite 3A as the adsorbent. Experimental investigations involve breakthrough analysis, cyclic operation (reaction and regeneration), and dynamic process evaluation using fully automated two-bed reactor columns. Theoretical models for conventional CO₂ hydrogenation processes (direct and indirect routes) are developed in Aspen Plus V14, while the SEDMES process is modelled in MATLAB by solving all governing equations. The obtained results from the theoretical analysis are validated using experimental data. Furthermore, Aspen Plus and MATLAB are integrated to conduct a comprehensive technical, economic, and environmental assessment.

Comparative analysis with equilibrium and plug flow reactor (PFR) models reveals that SEDMES significantly enhances process performance. At 85 s of reaction time, DME production in the SEDMES process achieves 53%, compared to only 2% in the PFR. CO₂ conversion rates for equilibrium, PFR, and SEDMES processes are calculated as 35%, 22%, and 55%, respectively. DME yield in the equilibrium and SEDMES processes is approximately three and ten times higher than in the PFR, with SEDMES also demonstrating substantially improved selectivity. These findings underscore the considerable potential of the SEDMES process as an efficient and effective alternative for CO₂ utilization in DME production. Further investigations into its energy efficiency, economic viability, and environmental impact are crucial to evaluating its industrial-scale implementation.

References

[1] Agency, I.E., 2023, International Energy Agency (IEA) Paris.

[2] Fleisch, T. et. al. Journal of Natural Gas Science and Engineering, 2012. 9: p. 94-107.