Synthesis of ethanol from syngas over Rh/Ce₁₋ₓZrₓO₂ catalysts

• Published in: Catalysis today 2011-04, Vol.164 (1), p.308-314
• Main Authors: Liu, Yanyong, Murata, Kazuhisa, Inaba, Megumu, Takahara, Isao, Okabe, Kiyomi
• Format: Article
• Language: English
• Subjects: acetaldehyde; acidity; Catalysis; catalysts; catalytic activity; Chemistry; coprecipitation; ethanol; Exact sciences and technology; General and physical chemistry; ions; methanol; particle size; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2010.10.087

Rh/Ce₁₋ₓZrₓO₂ (x=0–1) samples (with 2wt% Rh loading) were prepared by a coprecipitation method using NH₃·H₂O as a precipitant. The resultant samples were used as catalysts for the synthesis of ethanol from syngas in a high-pressure fixed-bed flow reactor under typical reaction conditions of T=548K, P=2.4MPa, H₂/CO=2/1, and W/F=10ghmol⁻¹. XRD results indicated that Zr⁴⁺ ions entered in the CeO₂ lattices when x was less than 0.2 in Rh/Ce₁₋ₓZrₓO₂. TPR results indicated that the reducibility of CeO₂ increased by inducing Zr⁴⁺ ions into the CeO₂ lattices in Rh/Ce₀.₈Zr₀.₂O₂. NH₃-TPD and CO₂-TPD results indicated that Rh/Ce₀.₈Zr₀.₂O₂ contained both acid sites and base sites on the surface. Rh/CeO₂ showed a CO conversion of 23.7%, which was higher than those over Rh/SiO₂ (10.1%), Rh/MgO (10.8%), and Rh/ZrO₂ (18.2%) at 548K because a strong interaction between support and metal (SISM) existed in Rh/CeO₂. Moreover, the CO conversion over Rh/Ce₀.₈Zr₀.₂O₂ (27.3%) was higher than that over Rh/CeO₂ (23.7%) due to the smaller Rh particle size and the stronger reducibility in Rh/Ce₀.₈Zr₀.₂O₂. The main oxygenated products were acetaldehyde and ethanol over neutral or acidic supports supported Rh catalysts (Rh/SiO₂, Rh/ZrO₂), and were methanol and ethanol over basic supports supported Rh catalysts (Rh/MgO, Rh/CeO₂, Rh/Ce₀.₈Zr₀.₂O₂). Rh/Ce₀.₈Zr₀.₂O₂ showed the highest selectivity for ethanol among various catalysts because the Ce₀.₈Zr₀.₂O₂ support simultaneously possesses reducibility, acidity and basicity.