Low-temperature methanation of syngas in slurry phase over Zr-doped Ni/γ-Al2O3 catalysts prepared using different methods

•Two types of catalysts were prepared by impregnation (IP) and impregnation coprecipitation (ICP) methods.•ICP catalyst showed better performance of methanation than that of IP catalyst in slurry reactor.•ICP method is favor for the formation of small size Ni particles and more reducible NiO.•Zr doping can moderate the interaction between Ni and γ-Al2O3 support and promote the dispersion of Ni.

Syngas methanation was performed at 280–330 °C in a stirred-slurry reactor with Zr-doped Ni/γ-Al2O3 catalysts. The catalysts were prepared using impregnation (IP) and impregnation–coprecipitation (ICP) methods. The catalyst 25Ni3Zr/γ-Al2O3 (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 °C under 1.5 MPa pressure, with a syngas flow of 10,000 mL g−1 h−1. However, the selectivity of CH4 over 25Ni3Zr/γ-Al2O3 (ICP) was 85.2%, which was slightly lower than that of 25Ni3Zr/γ-Al2O3 (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-Al2O3 support by the ICP method. Zr doping improved Ni dispersion and H2-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.

Graphical abstractThe catalyst 25N3ZA prepared by impregnation co-precipitation(ICP) shows higher activity of methanation than that of impregnation (IP), and its CO conversion of CO was as high as 91.2% at reaction conditions of 325 °C, 10,000 mL g−1 h−1 and 1.5 MPa. Superior performance can be attributed to (i) better dispersion of Ni on the γ-Al2O3 support by ICP; (ii) Zr doping improved the dispersion of Ni as well the hydrogen-promoted dissociation of CO.Figure optionsDownload full-size imageDownload as PowerPoint slide