Properties of Sm2O3–ZrO2 composite oxides and their catalytic performance in isosynthesis

Abstract

Sm 2 O 3 doped ZrO 2 -based catalysts (Sm 2 O 3 –ZrO 2 composite oxide) were prepared by co-precipitation and their physical properties (texture and structure) and chemical properties (acid–base and redox) were characterized with the methods of N 2 adsorption–desorption isotherm, powder X-ray diffraction, Raman spectroscopy, NH 3 and CO 2 temperature programmed desorption and H 2 temperature programmed reduction. The catalytic performances of the catalysts (activity and selectivities) were evaluated in the CO hydrogenation to isobutene and isobutane (isosynthesis) under the reaction conditions of 673 K, 5.0 MPa, and 650 h −1 . The relationship between the catalytic performance and the physical/chemical properties of Sm 2 O 3 –ZrO 2 catalysts were also examined. The catalytic activity and selectivity of the Sm 2 O 3 –ZrO 2 catalysts varied with Sm 2 O 3 doping. The physical properties of the catalysts, such as cumulative pore volumes, average pore diameters and crystal sizes had some influences on the activity and selectivity in the isosynthesis. CO conversion increased with an increase in the amount of the acidic sites on the surface of Sm 2 O 3 –ZrO 2 catalysts, while iso -C 4 percentage in total hydrocarbons increased with an increase in the amount of the basic sites. The addition of Sm 2 O 3 into ZrO 2 enhanced the reducibility of Sm 2 O 3 –ZrO 2 catalysts. The highest CO conversion (21.6%) and C 4 selectivity (41.8%) were obtained over the catalyst that had a maximum amount of H 2 consumptions (57.7 μmol g −1 ) in the TPR measurement for Sm 2 O 3 –ZrO 2 catalysts. A coordination of the acid–base properties and the redox property may play important role for the improvement of the catalytic performances of the isosynthesis. Sm 2 O 3 –ZrO 2 composite oxides were prepared by co-precipitation, characterized with the methods of N 2 adsorption desorption isotherm, powder X-ray diffraction, Raman spectra, NH 3 and CO 2 temperature programmed desorption and H 2 temperature programmed reduction, and evaluated as the catalysts in the isosynthesis under the reaction conditions of 673 K, 5.0 MPa and 650 h −1 .