Effects of calcination temperatures on the structure-activity relationship of Ni-La/Al 2 O 3 catalysts for syngas methanation.

A series of Ni-La/Al 2 O 3 catalysts for the syngas methanation reaction were prepared by a mechanochemical method and characterized by thermogravimetric analysis (TG-DTA), X-ray fluorescence (XRF), X-ray diffraction (XRD), N 2 adsorption-desorption, H 2 temperature-programmed reduction (H 2 -TPR), and X-ray photoelectron spectroscopy (XPS). The calcination temperatures (350-700 °C) had significant impacts on the crystallite sizes and interactions between NiO and Al 2 O 3 . The catalyst calcined at 400 °C (cat-400) showed a 12.1% Ni dispersion degree and the maximum bound state of NiO (54%) through the Gaussian fitting of H 2 -TPR. Cat-400 also achieved the highest CO conversion, CH 4 selectivity and yield. Cat-400 exhibited good stability and catalytic activity in a lifetime testing of 200 h. The deactivation of cat-400 was mainly caused by carbon deposition according to the data from XRD, TG-DTG and XPS.