Ex-LDH-Based Catalysts for CO₂ Conversion to Methanol and Dimethyl Ether

• Main Authors: Mauro Mureddu, Sarah Lai, Luciano Atzori, Elisabetta Rombi, Francesca Ferrara, Alberto Pettinau, Maria Giorgia Cutrufello
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Catalysts
• Subjects: CO₂ hydrogenation; methanol synthesis; DME synthesis; ex-LDH; bifunctional catalysts
• Online Access: https://www.mdpi.com/2073-4344/11/5/615

CO₂-derived methanol and dimethyl ether can play a very important role as fuels, energy carriers, and bulk chemicals. Methanol production from CO₂ and renewable hydrogen is considered to be one of the most promising pathways to alleviate global warming. In turn, methanol could be subsequently dehydrated into DME; alternatively, one-step CO₂ conversion to DME can be obtained by hydrogenation on bifunctional catalysts. In this light, four oxide catalysts with the same Cu and Zn content (Cu/Zn molar ratio = 2) were synthesized by calcining the corresponding CuZnAl LDH systems modified with Zr and/or Ce. The fresh ex-LDH catalysts were characterized in terms of composition, texture, structure, surface acidity and basicity, and reducibility. Structural and acid–base properties were also studied on H₂-treated samples, on which specific metal surface area and dispersion of metallic Cu were determined as well. After in situ H₂ treatment, the ex-LDH systems were tested as catalysts for the hydrogenation of CO₂ to methanol at 250 °C and 3.0 MPa. In the same experimental conditions, CO₂ conversion into dimethyl ether was studied on bifunctional catalysts obtained by physically mixing the ex-LDH hydrogenation catalysts with acid ferrierite or ZSM-5 zeolites. For both processes, the effect of the Al/Zr/Ce ratio on the products distribution was investigated.