Nanoscale control during synthesis of Me/La2O3, Me/CexGd1−xOy and Me/CexZr1−xOy (Me = Ni, Pt, Pd, Rh) catalysts for autothermal reforming of methane

Abstract

Supported catalysts Me/La2O3, Me/CexGd1−xOy and Me/CexZr1−xOy (Me=Ni, Pt, Pd, Rh) were developed for the autothermal reforming of methane (ATR of CH4). The influence of support composition (La2O3, CexGd1−xOy, x=0.50–0.90 and CexZr1−xOy, x=0.33–0.67), type and content of the active component (5–30wt% Ni; 0.5–1.5wt% Pt, Pd or Rh) on the nanostructure of catalysts and their performance in the ATR of CH4 was investigated. The properties and structure of the catalysts in the course of their preparation and operation in the reaction were systematically characterized by means of X-ray diffraction, BET N2 adsorption/desorption, H2 temperature-programmed reduction, transmission electron microscopy and X-ray photoelectron spectroscopy techniques. The state and particle size of Ni-containing species were regulated by the support composition and Ni content. In case of the La2O3 support, the strong interaction between NiO and La2O3 led to the formation of two binary oxides LaNiO3 and La2NiO4 in the fresh samples, the composition of which was regulated by the Ni content. In case of the CexGd1−xOy and CexZr1−xOy supports, in contrast to the La2O3 support, nickel oxide and ceria-based solid solution were formed in the fresh samples. The catalyst evolution under reaction condition was studied. The conversion of methane and product (H2, CO) yields considerably increased when Ce0.8Gd0.2Oy or Ce0.5Zr0.5Oy instead of La2O3 were used as catalyst supports: at 850°C the yields of ∼35% H2 and ∼41% CO at CH4 conversion ∼76% were observed for the 10wt%Ni/La2O3, while the yields of ∼49% H2 and ∼66% CO at CH4 conversion ∼97% were observed for the 10wt% Ni/Ce0.5Zr0.5O2, which correlates with the increase of reducibility of Ni species as a result of weakening of the Ni–support interaction. The optimal value of metal content for the catalyst performance also depends on the support composition. The best ATR of CH4 performance is provided by 10wt% Ni/Ce0.5Zr0.5O2 and 1wt% Rh/Ce0.8Gd0.2O2 catalysts.