Abstract
Rh/Ce 1− x Zr x O 2 ( x = 0–1) samples (with 2 wt% Rh loading) were prepared by a coprecipitation method using NH 3·H 2O 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 = 548 K, P = 2.4 MPa, H 2/CO = 2/1, and W/ F = 10 g h mol −1. XRD results indicated that Zr 4+ ions entered in the CeO 2 lattices when x was less than 0.2 in Rh/Ce 1− x Zr x O 2. TPR results indicated that the reducibility of CeO 2 increased by inducing Zr 4+ ions into the CeO 2 lattices in Rh/Ce 0.8Zr 0.2O 2. NH 3-TPD and CO 2-TPD results indicated that Rh/Ce 0.8Zr 0.2O 2 contained both acid sites and base sites on the surface. Rh/CeO 2 showed a CO conversion of 23.7%, which was higher than those over Rh/SiO 2 (10.1%), Rh/MgO (10.8%), and Rh/ZrO 2 (18.2%) at 548 K because a strong interaction between support and metal (SISM) existed in Rh/CeO 2. Moreover, the CO conversion over Rh/Ce 0.8Zr 0.2O 2 (27.3%) was higher than that over Rh/CeO 2 (23.7%) due to the smaller Rh particle size and the stronger reducibility in Rh/Ce 0.8Zr 0.2O 2. The main oxygenated products were acetaldehyde and ethanol over neutral or acidic supports supported Rh catalysts (Rh/SiO 2, Rh/ZrO 2), and were methanol and ethanol over basic supports supported Rh catalysts (Rh/MgO, Rh/CeO 2, Rh/Ce 0.8Zr 0.2O 2). Rh/Ce 0.8Zr 0.2O 2 showed the highest selectivity for ethanol among various catalysts because the Ce 0.8Zr 0.2O 2 support simultaneously possesses reducibility, acidity and basicity.
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