Hydrogen Production from Biogas: Development of an Efficient Nickel Catalyst by the Exsolution Approach

Hydrogen production from biogas over alumina-supported Ce 1−x Ni x O 2−x catalysts was studied in a temperature range of 600–850 °C with an initial gas composition of CH 4 /CO 2 /H 2 O of 1/0.8/0.4. To achieve a high and stable hydrogen yield, highly dispersed Ni catalysts were prepared through the exsolution approach. A solid solution of Ce 1−x Ni x O 2−x was firstly formed on the surface of Al 2 O 3 and then activated in H 2 /Ar at 800 °C. The genesis and properties of the Ce 1−x Ni x O 2−x /Al 2 O 3 catalysts were established using X-ray fluorescence analysis, thermal analysis, N 2 adsorption, ex situ and in situ X-ray diffraction, Raman spectroscopy, electron microscopy, EDX analysis, and temperature-programmed hydrogen reduction. The performance of Ce 1−x Ni x O 2−x /Al 2 O 3 catalysts in biogas conversion was tuned by regulation of the dispersion and reducibility of the active component through variation of content (5–20 wt.%) and composition (x = 0.2, 0.5, 0.8) of Ce 1−x Ni x O 2−x as well as the mode of its loading (co-impregnation (CI), citrate sol–gel method (SG)). For the 20 wt.% Ce 1−x Ni x O 2−x /Al 2 O 3 catalyst, the rate of the coke formation decreased by a factor of 10 as x increased from 0.2 to 0.8. The optimal catalyst composition (20 wt.% Ce 0.2 Ni 0.8 O 1.8 /80 wt.% Al 2 O 3 ) and preparation mode (citrate sol–gel method) were determined. At 850 °C, the 20 wt.% Ce 0.2 Ni 0.8 O 1.8 /Al 2 O 3 -SG catalyst provides 100% hydrogen yield at full CH 4 conversion and 85% CO 2 utilization.