Supported nickel nanocatalysts for the dry reforming of methane: Effect of SBA-15's pore sizes on the catalytic performances of Nickel nanoparticles

Abstract

Mesoporous materials are interesting supports for the dispersion and the size control of metallic particles used as active phases of heterogeneous catalysts. The large porosity of such materials provides some confinement effect and physical barriers against sintering, which are expected to enhance the catalytic properties. In this work, a systematic study of the influence of the pore size on the performances of catalysts designed for the Dry Reforming of Methane reaction has been carried out. To do so, three siliceous SBA-15 supports (S4, S5, S7) with similar grain sizes (0.4-0.6 μm) but different mean pore diameters (4, 5, and 7 nm, respectively) were impregnated by an aqueous solution of nickel(II) nitrate in presence of pentane ("Two-solvents method", 5 wt.% of Ni). After calcination and reduction with H2, the smallest Ni particles were observed in the S7-based Ni catalyst (DNi = 5.4 nm), in contrast to the S4-based one (DNi = 7 nm). This is explained by an improved accessibility of the larger pores during the nickel impregnation step. As a consequence of this better metal dispersion, increasing the pores size of the siliceous support also led to an enhancement of the catalytic properties in terms of both activity and stability. In particular, the CH4 conversion increased from 63% (Ni/S4) to 75% (Ni/S7) at 650 °C under a GHSV of 72 L g-1 h-1.