(86e) CO2 Hydrogenation to Methanol Using Hybrid Flame-Made CuO/ZrO2 – Polymer Membrane Reactors

Methanol exhibits a range of advantages as a potential future fuel due to its high energy density compared to that of natural gas and hydrogen. Traditional methods of methanol synthesis by natural gas have a significant greenhouse gas footprint as they involve CO₂ release as a byproduct. An alternative approach to methanol production by natural gas, is CO₂ hydrogenation. However, high conversion of carbon dioxide into methanol presents significant challenges, primarily arising from thermodynamic constraints and catalyst deactivation due to the formation of water as a by-product. So, research interest has focused on the development of new catalysts, such as Cu/ZrO₂ (Kattel et al., 2016), Cu/ZnO/ZrO₂ (Witoon et al., 2018), and Cu/ZnO/Al₂O₃ (Tada et al., 2017), that are both active to CO₂ hydrogenation and selective to methanol.

In response to this challenge, hybrid nanoparticle-membrane nanocomposites are manufactured in this work via direct one-step deposition. CuO/ZrO₂ nanoparticles are produced by flame spray pyrolysis (FSP) at various precursor solution-to-oxygen (P/O) flow rate ratios and are deposited on polymeric membranes highly selective to methanol (Figure 1a). Figure 1b and c shows scanning electron microscopy (SEM) images of flame-made CuO/ZrO₂ catalyst produced at a P/D ratio of (b) 2 mL/min precursor solution to 8 L/min oxygen (2/8, cold flame) and (c) 10/8 (hot flame), deposited on 6FDA-TMPDA membranes. Increasing the precursor flow rate, leads to higher temperature and longer high-temperature particle residence time, which in turn results in larger CuO and ZrO₂ crystal size and smaller specific surface area.

The effect of nanoparticle and film characteristics on the CO₂ conversion and methanol production rate is quantified. FSP conditions leading to nanocatalysts with highly activity to CO₂ hydrogenation are identified, while the selectivity to methanol, which is enhanced by the presence of polyimide membranes, is also evaluated. At 200 °C and 20 bar, these catalytic membrane reactors demonstrate exceptional performance, achieving 113% improvement in carbon dioxide conversion and a remarkable 106% increase in methanol production rate (Figure 1d) compared to conventional catalytic fixed bed reactors (Fig. 1d: horizontal line). Overall, the catalyst-membrane reactors have shown long-term stability and ability to suppress catalyst deactivation caused by water, ensuring sustained catalyst stability throughout the reaction.

Such hybrid membrane-catalytic nanoparticle reactors are a promising technology which enables industries to convert their carbon dioxide wastes into valuable energy products, such as methanol.

Funded by Future Fuels Cooperative Research Centre grant (RP1.3-04) and the University of Melbourne, Australia.

References

Kattel, S., Yan, B., Yang, Y., Chen, J. G., and Liu, P. (2016). J. Am. Chem. Soc. 138: 12440-12450.

Witoon, T., Numpilai, T., Phongamwong, T., Donphai, W., Boonyuen, C., Warakulwit, C., Chareonpanich, M., and Limtrakul, J. (2018). J. Chem. Eng. 334: 1781-1791.

Tada, S., Watanabe, F., Kiyota, K., Shimoda, N., Hayashi, R., Takahashi, M., Nariyuki, A., Igarashi A., Satokawa, S. (2017). J. Catal. 351: 107-118.