Porous clay minerals: active, selective and stable catalysts for isopropanol conversion to propylene
Résumé
Propylene, used in the production of polypropylene, acrylonitrile, acrylic acid, acrolein, propylene oxide and glycols, is conventionally manufactured from fossil raw materials. To face the challenges of propylene demand growth (1) and environmental concern, alternative sustainable synthesis routes based on renewable sources have become of interest. In this work, isopropanol catalytic dehydration is studied as a potentially effective alternative to catalytic/steam cracking of fossil feedstocks to produce propylene. Although well known to the catalysis world, this process is almost not used at an industrial scale due to the formation of side products (particularly di-isopropyl ether and n-propanol). Large-scale application of the process requires optimized catalysts with adapting properties including high activity, specific acidity and porous structure as well as resistance to steam (2). Claystones are widely used industrially as adsorbents, catalysts or catalyst supports due to their unique properties such as the swelling capacity in water, stability, high surface area and multimodal porous structure (3,4) and, therefore, could be promising catalysts for this application. To this end, commercial clay minerals were deeply characterized by X-ray diffraction, N2 adsorption isotherms at -196°C, X-ray fluorescence, thermogravimetric analysis, scanning and transmission electron microscopy. The catalysts have been screened based on their acid/base properties as determined by adsorption microcalorimetry of NH3 and SO2 at 150°C and on the impact of steam on their physio-chemical characteristics. The applicability of such materials in isopropanol selective conversion will be discussed based on their structural features, stability and the amount and distribution of active sites. References (1) Phung, T. K.; Pham, T. L. M.; Vu, K. B.; Busca, G. (Bio)Propylene Production Processes: A Critical Review. J. Environ. Chem. Eng. 2021, 9 (4), 105673. https://doi.org/10.1016/j.jece.2021.105673. (2) Dubois, J.-L.; Postole, G.; Silvester, L.; Auroux, A. Catalytic Dehydration of Isopropanol to Propylene. Catalysts 2022, 12 (10), 1097. https://doi.org/10.3390/catal12101097. (3) Zhao, H.; Zhou, C. H.; Wu, L. M.; Lou, J. Y.; Li, N.; Yang, H. M.; Tong, D. S.; Yu, W. H. Catalytic Dehydration of Glycerol to Acrolein over Sulfuric Acid-Activated Montmorillonite Catalysts. Appl. Clay Sci. 2013, 74, 154–162. https://doi.org/10.1016/j.clay.2012.09.011. (4) Al-Ani, A.; Gertisser, R.; Zholobenko, V. Structural Features and Stability of Spanish Sepiolite as a Potential Catalyst. Appl. Clay Sci. 2018, 162, 297–304. https://doi.org/10.1016/j.clay.2018.06.021. Acknowledgements This work is part of PYROCO2 project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101037009