Effect of La_2O_3 promoter on NiO/Al_2O_3 catalyst in CO methanation

摘要

A series of NiO/Al_2O_3 catalysts promoted by different La_2O_3 contents were prepared by impregnation method. The physicochemical properties of NiO-La_2O_3/Al_2O_3 were characterized by N_2 adsorption-desorption, X-ray diffraction (XRD), H_2 temperature programmed reduction (H_2-TPR) and H, chemisorption. The effect of La_2O_3 on the activity of NiO/Al_2O_3 for CO methanation was investigated in a fixed bed reactor. A lifetime test, as well as thermogravimet-ric (TG) analysis, was performed to investigate the stability performance and anti-carbon deposition of catalysts. The results showed that the addition of La_2O_3 can restrain the growth of NiO particles, increase the H_2 uptake and Ni dispersion, and therefore enhance the activity of catalysts. When the La_2O_3 content was 3 wt%, a CO conversion of 98% and a selectivity to CH_4 of 96% were obtained at 400 ℃. Furthermore, the catalyst NiO-La_2O_3/Al_2O_3, with 3 wr% La_2O_3 content displayed highly stable performance in long-term tests, especially exhibiting good anti-carbon deposition property.