Hydrogen production through autothermal reforming of CH4: Efficiency and action mode of noble (M = Pt, Pd) and non-noble (M = Re, Mo, Sn) metal additives in the composition of Ni-M/Ce0.5Zr0.5O2/Al2O3 catalysts

Abstract

Hydrogen production through autothermal reforming of methane (ATR of CH4) over promoted Ni catalysts was studied. The control of the ability to self-activation and activity of Ni-M/Ce0.5Zr0.5O2/Al2O3 catalysts was achieved by tuning their reducibility through the application of different types (M = Pt, Pd, Re, Mo or Sn) and content (molar ratio M/Ni = 0.003, 0.01 or 0.03) of additive. The comparison of the efficiency and action mode of noble (M = Pt, Pd) and non-noble (M = Re, Mo, Sn) metal additives in the composition of Ni-M/Ce0.5Zr0.5O2/Al2O3 catalysts was performed using X-ray fluorescence analysis, N2 adsorption, X-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction with hydrogen, and thermal analysis. The composition-characteristics-activity correlations were determined. It was shown that the introduction of a promoter does not affect the textural and structural properties of catalysts but influences their reducibility and performance in ATR of CH4. At the similar dispersion of NiO active component (11 ± 2 nm), the Ni2+ reduction is intensified in the following order of additives: Mo < Sn < Re ≤ Pd < Pt. It was found that for the activation of Ni and Ni–Sn catalysts before ATR of CH4 tests, the pre-reduction is required. On the contrary, the introduction of Pt, Pd and Re additives leads to the self-activation of catalysts under the reaction conditions and an increase of the H2 yield due to the enhanced reducibility of Ni2+. The efficient and stable catalyst for hydrogen production has been developed: in ATR of CH4 at 850 °C over an optimum 10Ni-0.9Re/Ce0.5Zr0.5O2/Al2O3 catalyst the H2 yield of 70% is attained. The designed catalyst has enhanced stability against oxidation and sintering of Ni active component as well as high resistance to coking.