The aqueous phase reforming (APR) of sugars and polyols into useful chemicals and fuels can be performed with nickel based catalysts as an alternative to commonly used platinum catalysts, however the loss of dispersion as a result of nickel particle growth is hindering the successful application of these catalysts. We have investigated the growth process of nickel catalysts on various support materials (CNF, ZrO2, SiC, γ-Al2O3 and α-Al2O3) and with various initial nanoparticle sizes under APR conditions. Nickel with different initial nickel particle sizes and loadings supported on α-Al2O3 revealed that the initial particle size is an important parameter determining the rate and extend of particle growth. Faster and more extensive particle growth was observed for a Ni/α-Al2O3 catalyst with an initial average particle size of 12 nm versus 20 nm (fig 1). Also, the catalyst with initially smaller particles was found to outgrow the catalyst with the larger particles. Varying extents of Ni particle growth were found for the different support materials but a possible support effect was overshadowed by the effect of the difference in initial particle sizes. Ostwald ripening is thought to be the most likely particle growth mechanism and it is postulated that the observed growth behaviors could be related to both the increased susceptibility of smaller nickel particle with respect to oxidation and to the higher driving force of smaller particles for growth.

Initial particle size effects on the stability of nickel catalysts in aqueous conditions

256th National Meeting (2018)

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