Low-temperature methanation of syngas in slurry phase over Zr-doped Ni/γ-Al_2O_3 catalysts prepared using different methods

摘要

Syngas methanation was performed at 280-330 ℃ in a stirred-slurry reactor with Zr-doped Ni/γ-Al_2O_3 catalysts. The catalysts were prepared using impregnation (IP) and impregnation-coprecipitation (ICP) methods. The catalyst 25Ni3Zr/γ-Al_2O_3 (ICP) had relatively high activity in syngas methanation and the water gas shift (WGS) reaction. A high CO conversion, ～91.2%, was obtained at 325 ℃ under 1.5 MPa pressure, with a syngas flow of 10,000 mLg~(-1) h~(-1). However, the selectivity of CH_4 over 25Ni3Zr/γ-Al_2O_3 (ICP) was 85.2%, which was slightly lower than that of 25Ni3Zr/γ-Al_2O_3 (IP), because of enhancement of the WGS reaction. The catalysts were characterized using temperature-programmed reduction, X-ray diffraction, and transmission electron microscopy; the results indicated that Ni was well dispersed on the γ-Al_2O_3 support by the ICP method. Zr doping improved Ni dispersion and H_2-promoted dissociation of CO. Furthermore, it was found that the larger amount of reducible Ni formed using the ICP method gave a better catalytic performance.